Nonwoven fabrics are used in absorbent articles, such as sanitary products and disposable diapers, cleaning products, such as wipers, and medical goods, such as masks, and such products employ nonwoven fabrics with performance suitable for the purpose of the products and their intended location of use.
With absorbent articles, for example, it is necessary to employ nonwoven fabrics that expand and contract in response to bodily movement during wear or use, without creating an uncomfortable feeling for the user. Disposable diapers require nonwoven fabrics with high elasticity and strength sufficient to prevent tearing during extension, as well as satisfactory feel on the skin and air permeability.
When elastic fibers are used to impart elasticity to nonwoven fabrics, the elastic fibers generally have tack and high abrasiveness, which are known to impair the feel of the nonwoven fabric on the skin.
For example, Patent document 1 discloses a front sheet with an indented form, having excellent air permeability in the horizontal directions. The front sheet described in Patent document 1 is characterized by having a first fiber layer and a second fiber layer composed of fiber aggregates, by having the first fiber layer and second fiber layer laminated and partially heat sealed in a prescribed pattern, by forming in the first fiber layer elevated sections at locations other than the heat-fused sections between the first and second fiber layers, with the locations of the elevated sections that are adjacent to the heat-fused sections having their constituent fibers heat sealed together and thus having higher rigidity than the other locations of the elevated sections, and by having an air permeation volume of at least 10 mL/cm2/sec in the horizontal directions under a pressure of 10 cN/cm2.
However, the front sheet of Patent document 1 has a problem in that (i) because the elevated sections of the first fiber layer are formed by heat shrinkage of the second fiber layer, the distances between fibers in the second fiber layer are reduced as heat shrinkage occurs, thus lowering the air permeability of the sheet in the thickness direction. Another problem with the front sheet of Patent document 1 is that (ii) the second fiber layer comprising heat sealing fibers undergo melting during heat shrinkage, causing bonding between the fibers, and the front sheet is therefore hardened and less able to follow body movement, while also exhibiting inferior feel on the skin.